Pressure actuated switch



June 16, 1959 o. .1. SAHOLT PRESSURE ACTUATED SWITCH Fild NOV. 5, 1958 Tl N ho m 533 96 mm m8 9 WJ wm 3v L .Y a L m O W Nm on o T m m 2 mm N. 1 om mm m O on No B V mk mm A E to in w mm Q mm mm ow United States Pate PRESSURE ACTUATED SWITCH Orville J. Saholt, China Lake, Calif., assignor to the United States of America as represented by the Secretary of the Navy Application November 5, 1958, Serial No. 772,150

7 Claims. (Cl. 200-82) (Granted under Title 35, US. Code (1952), sec. 266) The invention described herein may be manufactured and used by or for the Government of the United States of America for governmental purposes without the payment of any royalties thereon or therefor.

The present invention relates to electrical switches and particularly to a miniature gas pressure actuated switch for closing an electrical circuit.

The pressure actuated switch of the present invention is a safety device for arming a rocket sustainer motor ignition circuit, or the like, such that the rocket booster motor must have ignited and then ceased to burn before the sustainer motor ignition circuit becomes electrically armed. The device comprises an electrical contact on the end of a spring biased gas operated piston which is prevented from closing by a pin on the piston bearing against and locking a torsionally spring loaded rotor. Prior types of gas pressure actuated switches are either in an open or a closed position before being actuated and then close or open, respectively, upon being actuated by gas pressure, and revert to their original position after the actuating gas pressure is reduced; thus, the prior art switches are open-closed-open or closed-open-closed type switches. The switch of the present invention is initially in a cocked open position. When it is pressure actuated the switch is uncocked, but remains in an open position. Only when the pressure drops does the switch move to a closed position; thus, the present switch is an open-open-closed type switch, unlike any prior switch.

It is an object of the invention, therefore, to provide an open-open-closed pressure actuated switch.

Another object of the invention is to provide a new and improved miniature gas pressure operated electrical switch.

A further object of the invention is to provide a normally open switch having a gas operated piston therein with means for preventing closing of the switch until after being pressure actuated and the actuating pressure is removed.

Other objects and many of the attendant advantages of this invention will be readily appreciated as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings wherein:

Fig. 1 is a cross-sectional longitudinal view of the pressure actuated switch of the present invention in its normal cocked and open position, prior to being actuated;

Fig. 2 is a cross-sectional view of the switch in its uncooked and open position while pressure is being applied against the spring loaded piston;

Fig. 3 is a cross-sectional view of the switch in its uncooked and closed position after the actuating pressure is removed from the piston;

Fig. 4 is a plan View of the rotor disc in the switch.

Referring now to the drawings, like numerals refer to like parts in each of the figures, and substantially all parts are circular in cross-section taken normal to the longitudinal axis of the views shown.

The entire switch assembly 10 is comprised of a minimum number of parts and is simple to operate. A housing cylinder 12 having an open end 14 and being closed at its opposite end with a base member 16 houses the entire operating or moving parts of the switch, as shown in Figs. 1, 2 and 3. A piston having a head portion 13 and a shaft portion 20 fits within housing cylinder 12. The diameter of head portion 18 is slightly less than the inner diameter of the housing cylinder, allowing the piston to slide therein. Head portion 18 of the piston has a circumferential groove 22 thereabout containing an O-ring 23 which slides against the inner surface of the housing cylinder to provide a gas seal for preventing gas from leaking past the piston head 18. An inwardly extending flange 24 is provided in the housing cylinder; the opening 26 formed thereby is slightly greater than the piston shaft 20, allowing the shaft to ride freely therein. Shaft 20 and aperture 26 are such as to prevent relative rotation thereof. A biasing spring 28 fits about piston shaft 20 and bears against flange 24 and the rear side of piston head 13 tending to move the piston in the direction of base member 16. The inner diameter of housing cylinder 12 at the closed end thereof is slightly enlarged to provide a seat 30 for holding rotor disc 32 which is free to rotate therein. Base member 16 holds rotor 32 in place and completely closes the end of housing cylinder 12 except for a passage 34 through the base member. Base member 16 may be mounted on the end of housing cylinder 12 by means of a crimp 36, as shown, or by any other suitable means. Passage 34 also extends through rotor 32 allowing gas under pressure, from an outside source not shown, to pass through the base member and rotor and enter the closed end of the cylinder housing. This gas pressure exerts a force on piston head 18 tending to move it in a direction against the force of biasing spring 28.

Piston head 18 has a pin-like protrusion 38 on the forward side thereof which fits into a cavity 40 on the surface of rotor 32 facing the piston head for holding the switch cocked in an open position. Protrusion or pin 38 is free to be lifted out of cavity 40 when the piston is moved back compressing biasing spring 28. Rotor 32 is torsionally spring loaded for rotation by means of a spring 42 which fits within a groove 44 on the inner surface of base member 16. The rotor is allowed to rotate a limited amount, 45 for example, when cocking pin 38 is removed from cavity 40. Rotor 32 also has a notch section 46 cut out of the side of the disc, as shown in Fig. 4, allowing a space for pin 38 to drop into after the rotor has moved and the gas pressure is removed.

On the opposite side of flange 24 from biasing spring 28 is a lower electrical switch contact 50 having substan tially the same diameter as the inner diameter of housing cylinder 12. A layer of insulating material 51 may be provided between contact 50 and housing 12. Lower contact 50 has an aperture 52 therethrough whose crosssection is that of a frustum of a cone; the smallest diameter of aperture 52 being equal to the diameter of aperture 26 formed by flange 24 so that piston shaft 20 will slide freely therein. End 54 of the piston, the opposite end from the piston head is slightly smaller in diameter than the main portion of piston shaft 20; it has mounted thereon the upper electrical switch contact 56, which may be insulated therefrom by a layer of insulating material 57. Upper contact 56 is in the shape of a frustum of a cone having a central aperture therethrough for mounting 54 of the piston shaft and is the same size as aperture 52 in lower contact 50, thus providing good electrical contact when upper contact 56 is moved to seat within aperture 52 in lower contact 50. Electrical lead wires 58 and 59 are electrically connected to upper and lower contacts 56 and 50, respectively.

The exterior configuration of housing cylinder 12 is not critical but it is preferably made from electrical insulating materials, though any other suitable materials may be used so long as the upper and lower contacts aresuitably insulated from each other when in open position. Copper is preferable for theupper and lower contact material though other suitable materials having'good electrical conductivity may be used.

The switch assembly of thepresent invention. opcrates as follows: Upper electrical contact 56 on the end of the gas operated piston is prevented from closing and contacting lowercontact 50 by rotor 32 which prevents the spring-loaded piston from going to the full down position, and is illustrated in Fig; 1. This is the normal open position of the switch and it is in this position that the switch is assembled. When gas pressure builds; up in an ignited rocket booster motor, for instance, the gas pressure may be used to move the piston upward, compressing biasing spring28, and removing pin 38 on .piston head 18 from cavity 40 in rotor 32; This allows the rotor, which is torsionally spring-loaded in its normal or initial position, to revolve approximately 45, for example. The switch is now in the armed oropen and uncooked position, as illustrated in Fig. 2. When the booster motor combustion gas pressure subsides, the biasing spring force drives the piston back down, past its original position to the fully closed position, thus closing the switch,

as illustrated in Fig. 3. This gives a switching sequence which is open when there is no pressure, open when it is subjected to'pressure, and closed when it returns to a no pressure condition.

Obviously, many modifications and variations of the present invention are possible in the light of the above teachings. the scope of the appended claims the invention may be practiced otherwise than as specifically described.

What is claimed is:

l. A pressure actuated switch comprising a housing, a base member closing one end of said housing, a bias spring and a piston within said housing, a torsionally loaded rotor means positioned between said piston and said base member, said bias spring biasing said piston against said rotor means preventing said rotor means from rotating, a first electrical contact carried on said piston, 21 second electrical contact mounted on said housing and operable to be contacted by said first electrical, contact, a passage into said housing for supplying gas under pressure for moving said piston, said piston initially being. held by said rotor means in a position operable to keep said first and second contacts separated,lmovement of said piston away from said rotormeans .by gas pressure being operable to allow said rotor means. to rotate. intoa position where subsequent subsidence of the gaspressure will allow said piston-to move toward saidbase member sufficiently for said first and second contacts to come into electrical contact with each other.

2. A pressure actuated switch comprising a tubular housing, a base member closing one end of said housing, a bias spring and a piston within said housing, a torsionally spring loaded rotor means positioned in said housing between said piston and said base member, said bias spring biasing said piston against said rotor means preventing said rotor means from rotating, a first electrical contact mounted on said-piston and-a second electrical contact mounted on said housing, said first electrical contact operable to be moved into contact with said second electrical contact, a passage into said housing for supplying gas under pressure for moving said piston, said piston initially being held by said rotor means in. a position operable.

to keepsaid first and second contacts separated, movementof said piston .away from said rotor meansby gas pressure being operable to allow said rotor means to ro tate into a position where subsequent subsidence of the It is therefore to be understood that within.

gas pressure will allow said piston to move toward said base member sufiicientlyfor said firstand second'contacts' saidpistonagainst said rotor means preventing said rotorfrom rotating, :1 first electrical contact mounted on said piston, a second electrical contact mounted on said hous-. ing, a passage into said housing for supplying gas under pressure formoving said'pistQn; said'pistoninitially being held by said rotor means in a position operable to reep said first and second contacts separated, movement of said piston bygas pressure being operable to allow said rotor means to rotate into a position where subsequent subsidence of the gas pressure will allow said piston to move toward said one end ofsaid housing sufficiently for said first and second contacts to come into electrical contact with each other.

4. A pressure actuated switch comprising a closed housing, a bias spring and a piston within said housing, a torsionally loaded rotor positioned between said piston and one end of said housing,,cooperating means on said piston and rotor which when engaged prevent said rotor from rotating, said bias spring biasing said piston against said rotor for engaging said cooperating means, a first electrical contact mounted on said piston, a second elcctri-I cal contact mounted on said housing, a passage into said' housing for supplying gas under pressure for moving said piston, said piston initially being held by said cooperating means on the piston and rotor in a position operable to keep said first and second contacts separated, movement of said piston by gas pressure being operable to disengage said cooperating means to allow said rotor to rotate into a position where subsequent subsidence of the gas pressure will allow said piston to move toward said one end of said housing sufficiently for said first and second contacts to come into electrical contact with each other.

5. A pressure actuated switch comprising a tubular housing, a base member closing one end of said housing,

a bias spring and a piston within said housing, a torsionally spring loaded rotor positioned in said housing between said piston and said base member, cooperating means on said piston and rotor which when engaged prevent said' rotor from rotating, said bias spring biasing said piston against said rotor for engaging said cooperating means, a first electrical contact mounted on said piston and a second electrical contact mounted on said housing, said first electrical contact operable to be moved into contact with. said second electrical contact, a passage into said housing for supplying gas under pressure for moving said piston, said piston initially being held by the cooperating means on the piston and rotor in a position operable to keep said first and second contacts separated, movement of said piston away from said rotor by gas pressure being operable to disengage said cooperating means to allow said rotor to rotate into a position where subsequent subsidence of the gas pressure will allow said piston to move toward said base member sufliciently for said first and second contacts to come into electrical contact with each other for completing an electrical circuit.

6. A pressure actuated switch as in claim-5 wherein agas pressureseal ring is provided about said piston to prevent gas leakage past-the piston.

7. A pressure actuated switch as in claim 5 wherein said.

first electrical contact is in the shape of a frustum of a cone and said second electrical contact has. an aperturetherein in the shape of a frustum of a cone the same size as saidfirst electrical contact,.when said contactscome;

into electrical contact saidfirst contact seats in the apera ture .in said second contact.

No references cited. 

